10,285 research outputs found
A philosophical context for methods to estimate origin-destination trip matrices using link counts.
This paper creates a philosophical structure for classifying methods which estimate origin-destination matrices using link counts. It is claimed that the motivation for doing so is to help real-life transport planners use matrix estimation methods effectively, especially in terms of trading-off observational data with prior subjective input (typically referred to as 'professional judgement'). The paper lists a number of applications that require such methods, differentiating between relatively simple and highly complex applications. It is argued that a sound philosophical perspective is particularly important for estimating trip matrices in the latter type of application. As a result of this argument, a classification structure is built up through using concepts of realism, subjectivity, empiricism and rationalism. Emphasis is put on the fact that, in typical transport planning applications, none of these concepts is useful in its extreme form. The structure is then used to make a review of methods for estimating trip matrices using link counts, covering material published over the past 30 years. The paper concludes by making recommendations, both philosophical and methodological, concerning both practical applications and further research
Nanomedicine and Society
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110021/1/cptclpt2008276.pd
Structure-property and composition-property relationships for poly(ethylene terephthalate) surfaces modified by helium plasma-based ion implantation
The surfaces of untreated and helium plasma-based ion implantation (He PBII) treated poly(ethylene terephthalate) (PET) samples were characterised by reflectance colorimetry, contact angle studies and measurements of surface electrical resistance. The results were related to the structural and compositional data obtained by the authors earlier on parallel samples by XPS and Raman spectroscopy. Inverse correlations between lightness and ID/IG ratio and between chroma and ID/IG ratio were obtained, suggesting that the PBII-treated PET samples darken and their colourfulness decreases with the increase of the portion of aromatic sp2 carbon rings in the chemical structure of the modified layer. Direct correlation between water contact angle and the ID/IG ratio and inverse correlations between surface energy and ID/IG ratio and between dispersive component of surface energy and ID/IG ratio were found, reflecting that surface wettability, surface energy and its dispersive component decrease with the formation of surface structure, characterised again by enhanced portion of aromatic sp2 carbon rings. The surface electrical resistance decreased with the increase of the surface C-content determined by XPS and also with the increase of the surface concentration of conjugated double bonds, reflected by the increase of the pi-pi* shake-up satellite of the C 1s peak
Simple matrix models for random Bergman metrics
Recently, the authors have proposed a new approach to the theory of random
metrics, making an explicit link between probability measures on the space of
metrics on a Kahler manifold and random matrix models. We consider simple
examples of such models and compute the one and two-point functions of the
metric. These geometric correlation functions correspond to new interesting
types of matrix model correlators. We study a large class of examples and
provide in particular a detailed study of the Wishart model.Comment: 23 pages, IOP Latex style, diastatic function Eq. (22) and contact
terms in Eqs. (76, 95) corrected, typos fixed. Accepted to JSTA
Crystal structure and functional analysis of Drosophila Wind, a protein-disulfide isomerase-related protein
An all-electric single-molecule hybridisation detector for short DNA fragments
In combining DNA nanotechnology and high-bandwidth single-molecule detection in nanopipettes, we demonstrate an all-electric, label-free hybridisation sensor for short DNA sequences (< 100 nt). Such short fragments are known to occur as circulating cell-free DNA in various bodily fluids, such as blood plasma and saliva, and have been identified as disease markers for cancer and infectious diseases. To this end, we use as a model system a 88-mer target from the RV1910c gene in Mycobacterium tuberculosis that is associated with antibiotic (isoniazid) resistance in TB. Upon binding to short probes attached to long carrier DNA, we show that resistive pulse sensing in nanopipettes is capable of identifying rather subtle structural differences, such as the hybridisation state of the probes, in a statistically robust manner. With significant potential towards multiplexing and high-throughput analysis, our study points towards a new, single-molecule DNA assay technology that is fast, easy to use and compatible with point of care environments
Recognizing Speech in a Novel Accent: The Motor Theory of Speech Perception Reframed
The motor theory of speech perception holds that we perceive the speech of
another in terms of a motor representation of that speech. However, when we
have learned to recognize a foreign accent, it seems plausible that recognition
of a word rarely involves reconstruction of the speech gestures of the speaker
rather than the listener. To better assess the motor theory and this
observation, we proceed in three stages. Part 1 places the motor theory of
speech perception in a larger framework based on our earlier models of the
adaptive formation of mirror neurons for grasping, and for viewing extensions
of that mirror system as part of a larger system for neuro-linguistic
processing, augmented by the present consideration of recognizing speech in a
novel accent. Part 2 then offers a novel computational model of how a listener
comes to understand the speech of someone speaking the listener's native
language with a foreign accent. The core tenet of the model is that the
listener uses hypotheses about the word the speaker is currently uttering to
update probabilities linking the sound produced by the speaker to phonemes in
the native language repertoire of the listener. This, on average, improves the
recognition of later words. This model is neutral regarding the nature of the
representations it uses (motor vs. auditory). It serve as a reference point for
the discussion in Part 3, which proposes a dual-stream neuro-linguistic
architecture to revisits claims for and against the motor theory of speech
perception and the relevance of mirror neurons, and extracts some implications
for the reframing of the motor theory
Heavy Majorana Neutrinos in the Effective Lagrangian Description: Application to Hadron Colliders
We consider the effects of heavy Majorana neutrinos N with sub-TeV masses. We
argue that the mere presence of these particles would be a signal of physics
beyond the minimal seesaw mechanism and their interactions are, therefore, best
described using an effective Lagrangian. We then consider the complete set of
leading effective operators (up to dimension 6) involving the N and Standard
Model fields and show that these interactions can be relatively easy to track
at high-energy colliders. For example, we find that an exchange of a TeV-scale
heavy vector field can yield thousands of characteristic same-sign lepton
number violating l^+ l^+ j j events (j=light jet) at the LHC if m_N < 600 GeV,
which can also have a distinctive forward-backward asymmetry signal; even the
Tevatron has good prospects for this signature if m_N < 300 GeV.Comment: 4 pages, 1 figur
Coercivity extrema in melt-spun CuCo ribbons: Effects of the magnetic moment distribution
Measurements of magnetization loops on melt-spun CuCo ribbons revealed a minimum in the temperature dependence of the coercivity. A coherent interpretation was given through Monte Carlo simulations of a dispersed system of noninteracting, uniaxial magnetic granules embedded in a nonmagnetic matrix. The coercivity is implicitly defined by the balance between the negative magnetization of superparamagnetic granules and the remaining magnetization of blocked granules after saturation in the positive field direction. When the temperature rises in a system made of a large amount of small granules and a small amount of big granules, unblocking predominates over thermal fluctuations and the coercivity decreases until a certain temperature at which most of the small granules are superparamagnetic; above this temperature, thermal fluctuations predominate, and the coercivity increases almost linearly with the temperature until the final unblocking of the big granules. (C) 1999 American Institute of Physics. [S0021-8979(99)04618-6].8663010301
Effects of electron-electron interactions on the electronic Raman scattering of graphite in high magnetic fields
We report the observation of strongly temperature-dependent, asymmetric
spectral lines in electronic Raman scattering spectra of graphite in a high
magnetic field up to 45 T applied along the c-axis. The magnetic field
quantizes the in-plane motion, while the out-of-plane motion remains free,
effectively reducing the system dimension from three to one. Optically created
electron-hole pairs interact with, or shake up, the one-dimensional Fermi sea
in the lowest Landau subbands. Based on the Tomonaga-Luttinger liquid theory,
we show that interaction effects modify the van Hove singularity to the form
at zero temperature. At finite temperature, we
predict a thermal broadening factor that increases linearly with the
temperature. Our model reproduces the observed temperature-dependent
line-shape, determining to be 0.05 at 40 T
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